| From the 1851 edition of the Manual of Magnetism:
Horizontal Beam Axial Engine. - An instrument in which there are
two horizontal beams, each connected with a bend bar moving in an upright
double helix, is represent [at the right]. The motion of the beams is communicated
to a single flywheel, by means of toothed wheels moved by cranks."
The cost was $15.00 to $18.00. This engine is in the Collection of Historical Instruments at Harvard University.
Palmer and Hall made a later version of this apparatus, with the main difference being in the shape of the walking beams.